I dropped out of MIT due to money -- I'd received no financial aid and no other assistance, and couldn't get loans (since I was under 18); I tried working and consulting to pay, but ended up about $50k behind in "late tuition payments". I had turned down full honors scholarships to other schools, mainly because I really wanted to go to MIT.

Luckily this was 1998 and I left to go start a crypto ecash startup in the Caribbean, first of several startups. I think 1 semester in a top school, then dropping out to do startups, might be a better education than enduring 4 years without really doing anything special. That said, I wish I had been able to complete a degree; I am 30 now and sometimes think about ether going back full-time to MIT, or doing a UK MBA, or taking classes at another school and then either finishing there or returning to MIT.

In retrospect, ROTC might have been the best option, but there were a few specific reasons I didn't do it at the time.